Multielectron reductions such as the hydrogen evolution reaction (HER) play an important role in the development of nowadays energy economy. Herein, the application of the organometallic approach as synthetic method allows obtaining very small, ligand-capped but also highly active ruthenium nanoparticles (RuNPs) for the HER in both acidic and basic media. When deposited onto glassy carbon, the catalytic activity of this nanomaterial in 1 M H2SO4 solution is highly dependent on the oxidation state of the NPs surface, with metallic Ru sites being clearly more active than RuO2 ones. In sharp contrast, in 1 M NaOH as electrolyte, the original Ru/RuO2 mixture is maintained even under reductive conditions. Estimation of surface active sites and electrochemically active surface area (ECSA) allowed benchmarking this catalytic system, confirming its leading performance among HER electrocatalysts reported at both acidic and basic pH. Thus, in 1 M NaOH condition, it displays lower overpotentials (η0 ≈ 0 mV, η10 = 25 mV) than those of commercial Pt/C and Ruthenium black (Rub), and also fairly outperforms them in short- and long-term stability tests. In 1 M H2SO4 solution, it clearly outdoes commercial Rub and is competitive or even superior to commercial Pt/C, working at very low overpotentials (η0 ≈ 0 mV, η10 = 20 mV) with a Tafel slope of 29 mV·dec–1, achieving TOFs as high as 17 s–1 at η = 100 mV and reaching a current density of |j| = 10 mA·cm–2 for at least 12 h without any sign of deactivation.

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Herein we present ruthenium nanoparticles (Ru-NPs) stabilized with two rigid NHC ligands derived from cholesterol. The obtained nanoparticles were fully characterized and applied in the hydrogenation of various aromatic compounds under mild conditions. Interestingly, the more bulky ligand gives a slightly lower ligand coverage and a faster catalyst.

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We present experimental and theoretical results for the transport of ions and molecules inside carbon nanotubes.

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A series of ruthenium nanoparticles (Ru NPs) bearing different ligands on their surfaces have been used as catalysts in the selective hydrogenation of nitrobenzene to cyclohexylamine. Ru-C60, Ru-PVP, Ru-HDA, and Ru-IPr [PVP = poly(vinylpyrrolidone); HDA = hexadecylamine, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene] have been chosen because of their different electronic properties, with HDA and IPr acting as donor ligands, PVP as a polymer with small interaction with the Ru NP surface, and fullerene C60 as an electron-attractor ligand, while their size and structure remain similar. A clear influence of the ligand on the Ru NP surface on the catalytic performances was obsd. The less donor ligands promote hydrogenation of the N-phenylhydroxylamine (PHA) intermediate, which is considered to be the rate-detg. step, leading to the more active catalysts, affecting also the chemoselectivity of the reaction. D. functional theory (DFT) calcns. show that the hydride coverage of the Ru NPs plays a key role in the adsorption of PHA on the surface of the NPs. This adsorption is indeed unfavored for realistic coverage values, higher than 1.5H/per surface Ru atom, explaining the accumulation of this intermediate under hydrogenation conditions, as obsd. with all Ru NPs here studied. In addn., DFT calcns. show that the adsorption of PHA is favored when fullerene C60 is present on the Ru NP surface compared to the uncapped Ru NPs, which correlates well with the higher turnover frequency obsd. for Ru-C60 catalyst compared to the other Ru NP systems bearing more donating ligands and also the higher selectivity obtained with this catalyst.

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